1. Field of the Invention
This invention relates generally to adjustable hydraulic dampers for vehicles and, more particularly, to a new and improved actuator for effecting adjustment.
2. Description of the Prior Art
In active suspension systems, the amount of damping provided by a vehicle's hydraulic dampers or shock absorbers is continuously adjustable during operation of the vehicle to provide optimum ride and/or handling. Typically, such systems include a plurality of sensors for detecting road conditions, an adjustable valve arrangement associated with each damper to vary the fluid flow characteristics thereof, and a preprogrammed on board control to adjust each valve arrangement in response to inputs provided by the sensors. Adjustable valve arrangements have been proposed wherein rotors on the shock absorber pistons or in side mounted housings are rotatable through a plurality of angularly spaced positions corresponding to different hydraulic damping capabilities. In one system, an electric motor driven gear train on the piston rod rotates a rotor mounted on the piston through a shaft extending down through the piston rod of the damper. In another system, a solenoid actuated plunger in a housing associated with the damper rotates a rotor in stepwise fashion between its control positions. In the former system, pressure spikes may temporarily immobilize the rotor on the piston and the actuator on the piston rod and a simple method of storing the control input to the rotor until mobility of the latter returns is absent. In the latter system, a space consuming side housing is required for the solenoid actuator. A rotary actuator according to this invention includes simple, economical, and novel structure for isolating the actuator from temporary immobility of the rotor and for storing the control input until mobility returns.